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| author | David Chase <drchase@google.com> | 2021-05-03 13:24:27 -0400 |
|---|---|---|
| committer | David Chase <drchase@google.com> | 2021-05-03 18:17:42 +0000 |
| commit | 8a4b7294af226f2628edc0ef2a7c45ecff6e06ff (patch) | |
| tree | 9aa2102a65a6579b507d9b31aeb63cefb26a9d89 /src/runtime | |
| parent | 7f9febd4a19a02bd25e40c63289268e9c062701e (diff) | |
| download | go-8a4b7294af226f2628edc0ef2a7c45ecff6e06ff.tar.gz go-8a4b7294af226f2628edc0ef2a7c45ecff6e06ff.zip | |
cmd/compile: fix possible nil deref added in CL 270943
In the event allocSpan returned a nil, this would crash.
Cleaned up the code and comments slightly, too.
Change-Id: I6231d4b4c14218e6956b4a97a205adc3206f59ec
Reviewed-on: https://go-review.googlesource.com/c/go/+/316429
Trust: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Diffstat (limited to 'src/runtime')
| -rw-r--r-- | src/runtime/mheap.go | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/src/runtime/mheap.go b/src/runtime/mheap.go index 952c0b21b0..84c00ce8f8 100644 --- a/src/runtime/mheap.go +++ b/src/runtime/mheap.go @@ -897,7 +897,8 @@ func (s spanAllocType) manual() bool { // spanclass indicates the span's size class and scannability. // // If needzero is true, the memory for the returned span will be zeroed. -// The boolean returned indicates whether the returned span is zeroed. +// The boolean returned indicates whether the returned span contains zeroes, +// either because this was requested, or because it was already zeroed. func (h *mheap) alloc(npages uintptr, spanclass spanClass, needzero bool) (*mspan, bool) { // Don't do any operations that lock the heap on the G stack. // It might trigger stack growth, and the stack growth code needs @@ -912,14 +913,15 @@ func (h *mheap) alloc(npages uintptr, spanclass spanClass, needzero bool) (*mspa s = h.allocSpan(npages, spanAllocHeap, spanclass) }) + if s == nil { + return nil, false + } isZeroed := s.needzero == 0 - if s != nil { - if needzero && s.needzero != 0 { - memclrNoHeapPointers(unsafe.Pointer(s.base()), s.npages<<_PageShift) - isZeroed = true - } - s.needzero = 0 + if needzero && !isZeroed { + memclrNoHeapPointers(unsafe.Pointer(s.base()), s.npages<<_PageShift) + isZeroed = true } + s.needzero = 0 return s, isZeroed } |